1. Field of the Invention
The invention relates to a three-dimensional display of an image by the parallax barrier system and, more particularly, to a method of three-dimensionally displaying an image by electrically generating a parallax barrier and an apparatus for such a method and also relates to a method of using such an apparatus.
2. Description of the Related Art
As a three-dimensional (hereinafter, also abbreviated to 3D) image display system which doesn,t need to use special glasses, there are several systems such as a lenticular system, a barrifocal mirror system, an integral photography system, a holography system, and so on. Among them, the present invention relates to the parallax barrier system. Therefore, the descriptions of the other systems are omitted because they are not directly concerned with the invention.
In the parallax barrier system, a stereogram display surface is observed by a viewer through a plurality of very thin vertical stripe-shaped aperture slits from the position which is away therefrom by only a predetermined distance. Elements of the image to be observed by both of the right and left eyes of the viewer are alternately displayed like vertical stripes onto the stereogram display surface. Such a construction is generally called a parallax stereogram. An amount of information recorded in the parallax stereogram is merely equal to the amount which corresponds to the right and left eyes, in other words, the amount which is twice as much as the information of a plane image. It cannot be always said, on the other hand, that the movement of a view point is also free. To eliminate the above drawbacks, therefore, W. Kanolt has proposed in 1918 a method of displaying a three-dimensional image which is named parallax panoramagram. According to such a method, in the parallax panoramagram, an aperture ratio of the aperture slit is reduced to a value within, for instance, about a range from 1/6 to 1/10 and images which have been photographed from many different directions are sequentially arranged like vertical stripes onto the stereogram display surface in units of elements of the images. At this time, a three-dimensional image of the directional resolution within a range from 6 to 10 is obtained.
The conventional 3D image display apparatus of the parallax barrier system, however, has the following problems. That is, when a new 3D image display apparatus will be used as a future 3D television display apparatus, it would be necessary that programs of the three- and two-dimensional display system could be displayed. 0n the other hand, when the new 3D image display apparatus is used as a display terminal of the computer graphics, CAD/CAM, or work station, it is necessary that the apparatus can display a 3D images. However, in the conventional 3D display apparatus of the parallax barrier system, the parallax barrier is generally formed on a film like and multi-directional continuous images which are displayed on the background of the barrier are observed through the barrier. Therefore, in such a conventional display apparatus, there is a problem such that when an ordinary 2D image is displayed on the display surface, the parallax barrier becomes an obstacle and the 2D image cannot be seen. That is, the conventional 3D image display apparatus of the parallax barrier system has a problem such that it doesn't have the compatibility with the 2D image display apparatus. Consequently, when the display apparatus should be commonly used as both of a 3D display terminal of the computer and a 2D image display apparatus like a television, a point regarding whether the display apparatus has the compatibility of the display such that the 2D image and/or 3D image can be displayed or not will be an extremely important problem in future. In addition, it is also demanded for the 3D display apparatus that both of the 3D image and the 2D image can be mixedly displayed in the same screen so as to correspond to multi-media.
In the conventional 3D image display apparatus of the parallax barrier system, after the shape, position, and the like of the barrier were once determined, they cannot be easily changed. In the conventional 3D display apparatus, it is impossible to dynamically cope with the change of an arbitrary number of view points from the double-eye system to the multi-eye system based on the number of observers.
The conventional parallax barrier system further has problems such that the vertical stripe-shaped aperture slits become an annoying and bothersome, an amount of light transmittance decreases due to the slits, and a bright stereoscopic image cannot be seen.